Semiconductor memory device, a sector-address conversion circuit, an address-conversion method, and operation method of the semiconductor memory device

ABSTRACT

The present invention aims at providing a semiconductor memory device that can be operational in a desired boot block mode, regardless of the original boot block type of the device, by facilitating rewriting of the memory device. A sector address from an outside source is inputted into a sector-address conversion circuit, which converts the sector address into an internal address, and a memory cell array is accessed through an address decoder circuit. Suppose that each of banks of the memory device is configured as a bottom boot type. By converting the sector address by the sector-address conversion circuit such that the sector-address now appears to the outside in the reverse order, each of the banks now functions as a top boot type.

CROSS-REFERENCE TO RELATED APPLICATIONS

This is a Continuation Application, which claims the benefit of pendingU.S. patent application Ser. No. 10/046,755 filed, Jan. 17, 2002. Thedisclosure of the prior application is hereby incorporated herein in itsentirety by reference.

BACKGROUND OF THE INVENTION

1. Field of the Invention

This invention relates to a semiconductor memory device, asector-address conversion circuit, an address-conversion method, and anoperation method of the semiconductor memory device.

2. Description of the Related Art

Various kinds of memory devices including a flash memory are known.Generally, the first operation at starting of a system, reset operationand the like is performed by reading a read-only boot program and thelike from a memory device.

Conventionally, a boot block used as an object for starting of a systemoccupies a small sector in a memory device, and is located in the highend or the low end of sector addresses (physical addresses) of thememory device (a bottom boot type or a top boot type, respectively, andcalled a boot block type) according to a requirement specification ofthe system. The two types are marketed as distinctly individualproducts.

FIG. 1A shows the top boot type memory device wherein a small sector 11located at the highest sector addresses of the memory device serves asthe boot block area.

FIG. 1B shows the bottom boot type memory device wherein a small sector16 located at the lowest sector addresses of the memory device serves asthe boot block area.

For an STB (set top box), there is a need to write new data whilekeeping data in a memory currently used in the system. That is, whenthere is an option service newly added and the like, it is necessary towrite data or a program transmitted from a circuit to the memory device,while watching television through a television circuit.

The STB has two memory devices 20 and 25 as shown in FIG. 2. The memorydevice 20 is rewritten using a program stored in a boot block area 26,keeping data in the memory device 25. Further, the memory device 25 issimilarly rewritten using a program stored in a boot block area 21,keeping data of the memory device 20. Thus, two memory devices are usedto rewrite contents of the other memory device alternately.

Moreover, as shown in FIG. 3, a memory device that has small sectors 31and 32 in the sectors of the highest addresses and the lowest addresses,respectively, is also available.

In addition, the boot program is stored in the lowest physical addressesof a memory device when the small sector is located in the lowestaddresses of the memory device. Moreover, the boot program is stored inthe highest physical addresses of a memory device when the small sectoris located in the highest addresses of the memory device.

However, rewriting of the data within the same system and the likealways requires to use the same boot block type from designrestrictions, and rewriting between memory devices with different bootblock types has a problem that it cannot be easily performed.

Moreover, a type of a memory device that has two or more banks, eachhaving a small sector that can be used as a boot block, and rewritingeach other is also marketed.

However, a problem with this type is that address areas of the bootblock differ (e.g. a bank or some banks are the top boot block type andthe other banks are the bottom boot block type), causing difficulties inrewriting the memory device.

SUMMARY OF THE INVENTION

It is a general object of the present invention to provide a device, acircuit, a method, and an operation method that substantially obviatesone or more of the problems caused by the limitations and disadvantagesof the related art.

Features and advantages of the present invention will be set forth inthe description which follows, and in part will become apparent from thedescription and the accompanying drawings, or may be learned by practiceof the invention according to the teachings provided in the description.Objects as well as other features and advantages of the presentinvention will be realized and attained by the device, the circuit, themethod, and the operation method particularly pointed out in thespecification in such full, clear, concise, and exact terms as to enablea person having ordinary skill in the art to practice the invention.

To achieve these and other advantages and in accordance with the purposeof the invention, as embodied and broadly described herein, theinvention provides a semiconductor memory device that can be operated asa desired boot block type irrespective of the original boot block typeof the memory device, and a circuit, a method and an operation methodtherefor.

In order to provide the above-mentioned subject, the present inventionadopts means as described hereunder.

The present invention enables easy rewriting of a memory whilemaintaining contents of another memory by splitting a semiconductormemory device (for example, a flash memory) into a plurality of areas(for example, banks) wherein the plurality of the areas accommodate aplurality of small sectors in the highest or the lowest physical addressin each area or in a series of a plurality of the physical addressescontaining the highest or the lowest physical address in the area,respectively.

The present invention further enables conversion of a boot block type ofa semiconductor memory device that has a plurality of areas wherein aplurality of the small sectors are provided in addition to a pluralityof sectors larger than the small sectors. A desired block type can beassigned to each of the areas, regardless of the original boot blocktype of the memory device. In order to provide the conversion, thepresent invention provides an address-conversion circuit that converts asector address inputted from the outside to an internal address so thatall the plurality of the areas have the same boot block type.

The conversion circuit is structured such that a bottom signal or a topsignal is supplied to control the boot block type.

The conversion circuit can also be structured such that a boot blocktype specifying command is given to a control circuit.

In these manners, a sector address can be converted for a desired bootblock type easily.

The present invention provides a semiconductor memory device that can beused at the time of starting a system (at a power up, a rebooting, aresetting and the like) and rewriting by storing a rewriting program ora boot program in the small sector in the semiconductor memory device atany time.

The address conversion circuit is applicable to a semiconductor memorydevice having a plurality of sectors, each of which further has aplurality of sectors. Thereby, the sector address inputted from theoutside is converted by the address conversion circuit such that theplurality of the areas operate as the same boot block type.

The present invention also provides a sector-address conversion circuitthat includes sector-address input terminals, sector-address outputterminals, boot block type specifying terminals to specify the bootblock type of a memory device and sector-address conversion circuitswith a signal conversion circuit. The above-mentioned signal conversioncircuit converts a sector address impressed to the sector-address inputterminals, based on the most significant bit (for example, A19) and asignal impressed to the above-mentioned boot block type specifyingterminals. The above-mentioned sector-address conversion circuit makesthe memory device including the above-mentioned sectors to operate as adesired boot block type by outputting the sector-address converted bythe above-mentioned signal conversion circuit from the sector-addressoutput terminals.

The above-mentioned sector-address conversion circuit can be a controlcircuit of the semiconductor memory device, which may be structured suchthat a boot block type specifying command can be inputted.

The present invention provides a method to use the semiconductor memorydevice having two areas. That is, a rewriting program is loaded to asmall sector of one of the two areas, called the first area thatrewrites a uniform sector of the other area, called the second area,then the rewriting program is loaded to the small sector of the secondarea to rewrite the uniform sector of the first area.

BRIEF DESCRIPTION OF THE DRAWINGS

FIGS. 1A and 1B are illustrative drawings showing a conventional memorydevice of a top boot type and a bottom boot type, respectively;

FIG. 2 is a drawing showing rewriting of a memory device in an STB;

FIG. 3 is a drawing showing a memory device that has two small sectors,one at the least significant sector address, and the other at the mostsignificant sector address;

FIGS. 4A, 4B and 4C are drawings showing the principle of firstsector-address conversion;

FIGS. 5A, 5B and 5C are drawings showing the principle of secondsector-address conversion;

FIGS. 6A and 6B are drawings showing an example of sector-addressconversion;

FIGS. 7A, 7B and 7C are drawings showing an example of a sector-addresstranslation table;

FIGS. 8A and 8B are first drawings showing an example of asector-address conversion circuit;

FIG. 9 is a second drawing showing an example of the sector-addressconversion circuit;

FIG. 10 is a drawing showing a flash memory device and its controlcircuit;

FIG. 11 is a drawing showing a command and address conversion of a flashmemory; and

FIG. 12 is a drawing showing an example of an operation method of asemiconductor memory device.

DESCRIPTION OF THE PREFERRED EMBODIMENTS

In the following, an embodiment of the present invention will bedescribed with reference to the accompanying drawings.

First, the principle of the sector address conversion of the memorydevice of this invention will be described with reference to FIGS. 4A,4B and 4C and FIG. 5.

As shown in FIG. 4A, a sector address from the outside is inputted intoa sector-address conversion circuit 40. By the sector-address conversioncircuit 40, the address is converted into a sector address of theinternal address, and a memory cell array (memory device) is accessedthrough an address decoder circuit 41.

The memory device can be accessed from the outside as a top boot type ora bottom boot type memory device as required by the sector-addressconversion circuit 40, regardless of whether the memory device is(originally) a top boot type or a bottom boot type.

The memory device shown in FIG. 4B has two banks 48 and 49, each ofwhich includes a uniform sector 42 and a small sector 43. Since thelower part of the drawing represents LSB (Least Significant Bit) and theupper part represents MSB (Most Significant Bit), each bank isstructured as a bottom boot type.

Then, if the sector of the memory device is accessed in the order ofphysical addresses as shown by arrows 44 and 45, without using anaddress decoder circuit 41 (or without changing the address if theaddress decoder circuit 41 is used), the two banks 48 and 49 function asbottom boot type banks.

However, if the sector-address conversion circuit 40 changes the sectoraddress such that it appears to the outside that the address is set upin the order as shown by arrows 46 and 47, the two banks 48 and 49function as top boot type banks.

Thus, the present invention enables a memory device with a plurality ofsmall sectors to function as a plurality of devices with a top boot typeor bottom boot type by preparing the address-conversion circuit thatdefines a boot block area in one of the upper or the lower areas of thesector address of the memory device.

FIG. 5A describes a memory device with three units of the bottom boottype bank that is shown in FIG. 4B, and FIG. 5C describes a memorydevice with three top boot type banks. Here, although the embodiment isdescribed around a memory device with two or three banks, the number ofbanks in the present invention is not limited to two or three, but theinvention can apply to a memory device with any plurality of banks.

FIG. 5B shows a case where the memory device of FIG. 3 is divided intotwo banks. If viewed from a physical address, a bank 53 is a bottom boottype and a bank 54 is a top boot type. In contrast thereto, if theaddress is made to appear to the outside in the order as shown by arrows55 and 56 by using the sector-address conversion circuit 40, the banks53 and 54 function as the top boot type. If the address is made toappear in the order as shown by arrows 57 and 58, the banks 53 and 54function as the bottom boot type.

Conversion of the sector address in the case of FIG. 5B will bedescribed with reference to FIGS. 6A and 6B.

The memory device shown in FIG. 6A has a memory space of 8 Mb, forexample. The device has two boot blocks 59, each occupying 64 Kb (=8Kb×8) and defined as constituting a sector. The device also has 14uniform sectors 60, each occupying a capacity of 64 Kb.

Therefore, the memory device in the drawing has a total of 16 sectors,each having a 64 Kb capacity. Here, the address given in FIG. 6Arepresents a physical address. Since there are 16 sectors, a sectoraddress can be expressed by 4 bits.

The present embodiment expresses a sector address by 4 bits of 16^(th)through 19^(th) th bits of the address (here, referred to as A16 throughA19 for convenience). Moreover, as to the external address, an E isprefixed to be referred to as EA16 through EA19, and an I is prefixedinstead to the internal address to be referred to as IA16 through IA19.

According to this notation, the sector-address conversion circuit 40 isa circuit that converts the external addresses EA16 through EA19 intothe internal addresses IA16 through IA19, as shown in FIG. 6B. Theconversion may be performed with reference to a table as shown in FIGS.7A, 7B and 7C or by circuits as shown in FIGS. 8A and 8B and FIG. 9.

FIGS. 7A, 7B and 7C show translation tables for the address conversionusing a conversion table. FIG. 7C is the translation table, and FIG. 7Aand FIG. 7B are a summary thereof for the top boot type and the bottomboot type, respectively. Here, a sign “#” used in FIG. 7A and FIG. 7Bindicates an inverse. For example, “#EA19” represents an inverse of“EA19”, that is, if “EA19” is “1”, “#EA19” is “0”.

If a sector address is set up like 55 and 56 in FIG. 5B, the banks 53and 54 will function as the top boot type, and if the sector address isset up like 57 and 58, the banks 53 and 54 will function as the bottomboot type.

In addition, in the present embodiment, the external sector address bitsEA16, EA17, EA18, and EA19 express 16 addresses from 0000 (referencenumber 66) to 1111 (reference number 67). All addresses 61 belong to thebank 53, and their EA19 that is the most significant bit of the addressare “0”. All addresses 62 belong to the bank 54, and their EA19 are “1”.Therefore, the address bit EA19 identifies a corresponding bank.

That is, when the EA19 is “0”, an address belongs to the bank 53, andwhen the EA19 is “1”, the address belongs to the bank 54.

As mentioned above, the bank 53 is of the bottom boot type. If thebottom boot type is desired, the internal address shall be the same asthe external address. However, if the top boot type is desired foroperation of the bank 53, the sector address is set up like 56 in FIG.5B. The set up is realized by making the internal address bits IA16,IA17, and IA18 (63) to take an inverse value of the address bits ofEA16, EA17, and EA18, respectively.

Similarly, since the bank 54 is the top boot type, the same setup as theexternal address shall be applied if the top boot type is desired.However, in order to operate the bank 54 as the bottom boot type, thesector address is set up like 57 in FIG. 5B. To realize this, theinternal address bits IA16, IA17, and IA18 (64) should be converted toan inverse value of the address bits of EA16, EA17, and EA18,respectively.

The above describes how the tables of FIG. 7A, FIG. 7B and FIG. 7C areprepared and used.

FIG. 8A is an embodiment example of the conversion circuit shown inFIGS. 6A and 6B.

The conversion circuit includes a sector-address input terminal, asector-address output terminal, a boot block type specifying terminalthat specifies the boot block type of the memory device, and a signalconversion circuit. The conversion circuit converts a sector addressimpressed to the sector-address input terminal, based on the mostsignificant bit of the sector address and a signal impressed to the bootblock type specifying terminal such that the memory device that containsthe sector operates as a desired boot block type.

The circuit of FIG. 8A includes NOT circuits 70 and 71, AND circuits 72and 73, an OR circuit 74, XOR circuits 75, 76, and 77, sector-addressinput terminals 100-103, sector-address output terminals 110-113, andboot block type specifying terminals 104 and 105 (a top boot typespecifying signal input terminal and a bottom boot type specifyingsignal input terminal, respectively) that determine the boot block typeof the memory device.

This circuit converts the external address bits EA16, EA17, EA18, andEA19 to the internal address bits IA16, IA17, IA18, and IA19,respectively, as described above in reference with the tables in FIGS.7A, 7B and 7C.

As shown in FIG. 8B, the bottom signal is put to “H” when the bottomboot type is desired, and the top signal is put to “H” when the top boottype is desired. It is inhibited that both the bottom signal and the topsignal are put to “H” simultaneously.

In the above, operation of the sector-address conversion circuit in FIG.8A has been described, where the bottom signal and the top signal areinputted from an external terminal.

FIG. 9 shows another example of the sector-address conversion circuit.In this example, sector addresses are converted by inputting a specificcommand into a control circuit of the memory device.

The conversion circuit described in FIG. 9 includes an address buffer 80to store an address signal temporarily, an address pattern decoder 81 todecode a pattern of the address and obtain a timing signal, a controlcircuit 82 to control according to an inputted control signal, acommand, and the like, a timing control circuit 83 to adjust timing of alatch circuit, a command decoder, and the like by acquiring timing fromthe output of the address pattern decoder, an input buffer 84 to storean incoming signal temporarily, a latch circuit 85 to latch input data,and a command decoder 86 to decode a command.

The command decoder 86 outputs a sector-address conversion signal, basedon the address signal, CE (Chip Enable), OE (Output Enable), WE (WriteEnable), and data (DQ).

FIG. 10 shows an example of a flash memory and its control circuit,which include a column gating (Y-gating) circuit 88 to open and close aninput and an output of a column signal according to an output of acolumn address decoder (Y-decoder) 96, a cell matrix 89 which is a flashmemory, a state control and command register 90 to temporarily store acommand and to control according to an input signal, a command and thelike, an erase voltage generator 91 to generate the erase voltage forthe flash memory, a writing voltage generator 92 to generate the writingvoltage for the flash memory, a timer 93, a CE-OE logic circuit 94 togenerate a control signal according to the CE signal and the OE sign alreceived, an address latch 95 to latch the inputted address signal, thecolumn address decoder (Y-decoder) 96 to decode a column address, a lineaddress decoder 97 to decode a line address, an input/output buffer 98to temporarily store input/output data, and a data latch circuit 99 totemporarily latch the data.

In this configuration, the sector addresses are switched for a top boottype or a bottom boot type operation, by inputting data “AAH” to anaddress “AAAH” in the first bus cycle, inputting data “55H” to anaddress “555H” in the second bus cycle, and inputting data “2FH” to theaddress “AAAH” in the 3rd bus cycle in the case of a byte mode, as shownin a command list of FIG. 11.

Next, a description will follow concerning a usage of the semiconductormemory device (also applicable to a semiconductor memory devicefunctioning as two banks of the same boot block type using anaddress-conversion circuit) which has two banks (bank A and bank B) withthe same boot block type, having a small sector at the most significantor the least significant physical address of each bank in reference withFIG. 12.

First, a rewriting program is loaded to the small sector of the bank A(S11), then, the uniform sector of the bank B is rewritten using thisprogram (S12).

Subsequently, the process jumps to the bank B (S13) to load the rewiringprogram to the small sector of the bank B (S15), and the uniform sectorof the bank A is rewritten using this program (S16).

In this manner, new data can be rewritten easily while data ismaintained in the memory currently used within a system.

According to the present invention, rewriting of a memory device isfacilitated, and a memory device that operates as a desired boot blocktype irrespective of the original boot block type of the device becomesavailable.

Further, when a plurality of small sectors are present in a memorydevice, a plurality of memory units with the top boot block or thebottom boot block become available, by providing an address-conversioncircuit that defines an area of the boot block in the highest or in thelowest area of the sector address of the memory device. A system thatconventionally had to use two or more memory devices can now be built byone memory device.

Further, a system such as an STB and the like has conventionally beeninstalled with two or more memory devices so that new data can bewritten to a memory, while maintaining data to a memory currently used,by storing the rewriting program in each boot block to rewrite data ofthe other memory alternately. Now, one memory device can provide theequivalent memory configuration.

Further, the present invention is not limited to these embodiments, butvarious variations and modifications may be made without departing fromthe scope of the present invention.

The present application is based on Japanese priority application No.2001-016302 filed on Jan. 24, 2001, with the Japanese Patent Office, theentire contents of which are hereby incorporated by reference.

1. A Method of reading a program from a memory area having one or moresmall sectors, comprising: inputting a first sector addresscorresponding to a first type; converting the first sector address intoa second sector address corresponding to a second type which isdifferent from the first type; and accessing the memory area with thesecond sector address.
 2. The method of claim 1, wherein theinitialization program is a boot program.
 3. The method of claim 1,wherein the first type is a top boot type and the second type is abottom boot type.
 4. The method of claim 1, wherein the first type is abottom boot type and the second type is a top boot type.
 5. The methodof claim 1, wherein the reading the program is performed when startingor resetting a system.
 6. The method of claim 1, wherein the sectoraddress is supplied from external of the memory area.
 7. A method ofreading a program from a memory area having one or more small sectors,comprising: inputting a sector address; converting the sector addressbased on a signal or a command specifying a boot block type; andaccessing the memory area with the converted sector address.
 8. Themethod of claim 7, wherein the boot block type is a top boot type or asecond boot type.
 9. The method of claim 7, wherein the signal and thecommand are supplied from external of the memory area.
 10. A method ofrewriting data in a memory area being split into a first area and asecond area, each area having one or more small sector and one or moreuniform sectors which are larger than the small sectors, comprising:loading a rewriting program to the small sector of the first area;rewriting the uniform sector of a second area using said rewritingprogram stored in the first area; loading a rewriting program to thesmall sector of the second area; and rewriting the uniform sector of thefirst area using said rewriting program stored the second area.
 11. Themethod of claim 10, wherein the memory area is single memory device. 12.The method of claim 10, wherein the rewriting program is a boot program.13. A system comprising: a memory area having one or more small sectorsand one or more uniform sectors which are larger than the small sectors;an address conversion section converting a sector address based on asignal or a command specifying a boot block type; and a memory controlarea accessing the memory area with the converted sector address. 14.The system of claim 13, comprising: a source supplying a sector addressto the address conversion section.
 15. The system of claim 13,comprising: a source supplying the signal or the command specifying theboot block type to the address conversion section.
 16. The system ofclaim 13, comprising: a boot block type specifying terminal sourcesupplying the signal or the command specifying the boot block type. 17.The system of claim 13, wherein the boot block type is a top boot typeor a second boot type.